Jane Mayer’s New Yorker article last year about the remorse felt today by Trump’s ghostwriter, Tony Schwartz.

Cohn, the counsel to Sen. Joseph McCarthy during the anti-Communist witch hunts of the early 1950s, was Trump’s mentor until his death in 1986. After McCarthy fell from power, Cohn became a New York power broker, introducing Trump to politicians and helping him cut deals. Cohn was a shrewd, ruthless bully whose philosophy, Auletta wrote, amounted to this: “Everyone lies, smears, covers up, protects their friends. The rules of the game don’t count as much as winning.”

Sound familiar?

(Cohn was a liar to the end, dying of AIDS while publicly denying that he was gay.)

Trump adopted his role model’s attack-first-and-never-apologize tactics, on contemptible display last week with his vile slur against television anchor Mika Brzezinski. It’s easy to envision the embittered president raging late into the night about dishonorable enemies and feeble defenders, asking himself what Roy would do.

After the Watergate investigations brought down President Richard Nixon in 1974, Cohn said Nixon should have destroyed the White House tapes that were used against him. Today, as the beleaguered president stews in the White House channeling his mentor, he might hear, “Fire Mueller.” (That’s Robert Mueller, the special counsel investigating possible links between Trump and Russia and related matters.)

O’Brien, who spent a lot of time with Trump while writing his book in the early 2000s, chronicles Trump’s business dealings and duplicities, including his spectacular failures involving casinos, a professional football team, an airline and the Plaza Hotel.

“TrumpNation” also captures Trump’s disregard for truths — even his own. During the George W. Bush administration, the book recounts, Trump noted: “America went from a country of openness and somewhat complacent and free, to a country that sadly is perceived around the world as a bully. … We could have been a country where the world embraced us. And instead the world hates us.”

Five months into his own administration, global trust in the United States has plummeted.

Trump sued O’Brien, charging that the book understated his financial worth. The suit was dismissed, but dozens of Trump falsehoods emerged during a deposition.

In “The Art of the Deal,” Trump brags about using “truthful hyperbole.” In his White House, an aide used the phrase “alternative facts.” These are euphemisms for lying. In his book, he describes the way he plays the media: “The press is always hungry for a good story. The more sensational the better.” Maybe that was the idea behind his wild claim in March that President Barack Obama tapped his phones.

Trump had long said that “The Art of the Deal” was his favorite book. Then, courting evangelical voters during the presidential campaign, he demoted it to No. 2 behind the Bible.

Schwartz, who spent a year-and-a-half with Trump to write the book, now talks about the subject’s “complete lack of conscience.” He found Trump intellectually incurious and pathologically impulsive. It was, Schwartz told Mayer, “impossible to keep him focused on any topic other than his own self-aggrandizement for more than a few minutes.”

What was true in the 1980s remains true today. Just look at the president’s lack of interest in intelligence briefings and ignorance about the details of the huge Republican health-care bill now under consideration by the Senate.

These books and articles won’t tell you how Trump would react to a crisis on the Korean Peninsula, or shed light on his Russian financial ties or reveal how much he knew about Russian interference with the U.S. presidential election last year. They offer only the vaguest hints of how he might respond to a domestic tragedy like the 1995 bombing of a federal office building in Oklahoma City by an anti-government militant, or to the 2015 massacre by a white supremacist of black parishioners in a Charleston, South Carolina, church.

But they do provide insight into the character of the president of the U.S. And that’s where to find the answer to that question I keep hearing over the phone: “What’s wrong with Donald Trump?”

Albert R. Hunt is a Bloomberg View columnist. Previously he was a reporter, bureau chief and executive Washington editor at the Wall Street Journal.